Adds these helpful functions to underscore, and a few more that should be documented soon...
- pairs
- toObject
- unEscape
- isNotEmpty
- selectKeys
- removeKeys
- renameKeys
- nest
- splitKeys
- combine
- extend_r
- fill
- isLastEmpty
- merge
- zipMerge
- partition
- compress
- joinOn
- matchTo
- mapRenameKeys
- mapMerge
- mapNest
- mapCombine
- filter$
- map$
- juxtapose
- add
- subtract
- multiply
- divide
- lessThan
- greaterThan
- either